In the drilling and completion industry, the formation of boreholes for the purpose of production or injection of fluid is common. The boreholes are used for exploration or extraction of natural resources such as hydrocarbons, oil, gas, water, and alternatively for CO2 sequestration. Thereafter, a series of casing strings may be set in the borehole and cemented into place. Communication between the casing string annulus and subterranean reservoirs containing natural resources is necessary for any of the above noted activities.
Perforating is the process of piercing the casing wall and cement to provide openings through which formation fluids and gas may enter. Since the charges employed in perforating are very powerful, extreme care must be employed to assure no detonation can occur at the surface and that detonation can only occur below the surface. Also, it is desired that the gun fire at the proper depth, since early detonation will result in holes in the casing at undesirable depths. Further, if the guns do not fire for whatever reason such as mechanical problems and it becomes necessary to pullout out of the wellbore with the loaded guns, additional burdensome procedures are required as well as the added expense.
Prior art systems for preventing premature detonation of the downhole tools includes plugs which remain solid at surface temperature, but which melt at downhole temperatures, such as disclosed in U.S. Pat. No. 5,115,865 to Carisella et al. and U.S. Pat. No. 5,223,665 to Burleson et al. U.S. Pat. No. 5,346,014 incorporates a rotating plug, which is actuated by a thermally responsive torsion member.
As can be appreciated, premature actuation of the downhole tools, whether on surface or downhole, must be avoided. The art would be receptive to alternative devices and methods for blocking inadvertent ballistic transfer.